Polymerization catalysts

ABSTRACT

Highly active catalysts for the polymerization of olefins are disclosed. The catalysts are prepared by mixing a hydride or organometallic compound of a metal belonging to Groups I, II or III of the Mendelyeev Periodic Table with the product obtained by contacting an oxygenated Ti compound in which one or more Ti atoms are bound through oxygen atoms to organic radicals with an activated anhydrous Mg dihalide. The polymerization of ethylene by means of said catalysts is also disclosed.

This is a continuation of application Ser. No. 397,111 filed Sept. 13,1973 now abandoned, which in turn is a continuation-in-part of Ser. No.248,597, filed Apr. 28, 1972 and now abandoned which was a continuationof Ser. No. 22,011, filed Mar. 23, 1970 and now abandoned.

THE PRIOR ART

Ethylene has been polymerized and copolymerized by means of various typsof catalysts. One of the best known catalysts consists of or is formedby the product of reaction between a titanium or vanadium compound andan organometallic derivative of the metals of Groups I, II or III of the(Mendelyeev) Periodic System.

THE PRESENT INVENTION

This invention provides catalysts for the polymerization of olefinswhich are considerably more active than the catalysts of the prior artand by means of which it is possible to obtain an exceptional increasein the quantity of polymer produced with respect to the amount ofcatalyst used.

An application originating with our group discloses catalysts for thepolymerization of olefins which are highly active and which consist ofthe product obtained by mixing a hydride or organometallic compound of aGroup I, II or III metal with the product obtained by contacting atitanium or vanadium trihalide with a carrier consisting of anhydrous Mgor Zn chloride under conditions such that the Mg or Zn chloride isactivated, or with a carrier consisting of the Mg or Zn halide inpreactivated form.

We have now found that it is possible to obtain catalysts the activityof which, in olefin polymerization, is comparable to and in someinstances even superior to the activity of the catalysts described inthe aforesaid application, starting with oxygenated Ti compounds inwhich one or more Ti atoms are bound through oxygen atoms to organicradicals.

Examples of the useful oxygenated catalysts are, for instance, thefollowing:

Ti(O--iC₃ H₇)Cl₃ ; Ti₂ (O₂ C₆ H₄)Cl₆ ; Ti(O--_(n) C₄ H₉)₂ Cl₂ ; Ti(OC₂H₅)₃ Cl; Ti(O--iC₃ H₇)₄ ; Ti(OC₆ H₅)Cl₃ ; Ti(O--C₆ H₁₁)₂ Cl₂ ; Ti(O--CH₂--C₆ H₅)₃ ; Ti(O--CH₂ --CH₂ --C₅ H₄ N)₄ ; Ti₂ Cl₃ (OC₃ H₇)₃ ;Ti(O--C(CH₃)═CH--CO--CH₃)Cl₃ ; Ti(CH₃ COO)Cl₃ ; Ti(C₆ H₅ COO)Cl₃ ;Ti(O--CH₂ --CH₂ --OCH₃)₂ Br₂ ; Ti(O--C₆ H₄ OCH₃)₃ I; Ti(OC₆ H₄ Cl)Cl₃.

The catalysts of the present invention thus consist of the productobtained by mixing a hydride or an organometallic compound of a metalbelonging to Group I, II or III of the (Mendelyeev) Periodic System withthe product obtained by contacting an oxygenated Ti compound of the typeindicated above with a carrier consisting of or comprising an anhydrousMg halide, more particularly the chloride or bromide, under conditionssuch that activation of the Mg halide results, or by contacting theoxygenated Ti compound with an anhydrous Mg halide in pre-activatedcondition.

By "anhydrous Mg halide in activated form" we mean a halide in a formcharacterized in that in its X-ray spectrum the intensity of thediffraction line of greatest intensity in the spectrum of normal(non-activated) Mg halide is strongly decreased and there appears abroad halo which is not present in the spectrum of the normal Mg halide.

In the case of anhydrous Mg chloride the active form of this inventionis characterized in that in its X-ray spectrum the diffraction line atd=2.56 Å (which is most intense in the spectrum of the normal non-activeMgCl₂) is strongly decreased and there appears a broad halo identifiedas being comprised between d=2.56 Å and d=2.95 Å.

Similarly, the X-ray spectrum of the active form of MgBr₂ of theinvention is characterized by the fact that the diffraction line atd=2.93 Å (which is the most intense diffraction line appearing in thespectrum of normal, non-active MgBr₂) is strongly decreased in intensityand there appears a diffused halo appearing between d=2.80 Å and d=3.25Å.

According to a preferred embodiment of the invention, the supportedcatalyst-forming component is prepared by co-grinding a mixture of theoxygenated Ti compound with the anhydrous Mg halide for a time, andunder conditions, such that the anhydrous Mg halide is transformed tothe active form required for the practice of this invention.

The grinding is preferably carried out in a ball mill, with the mixturein dry condition, i.e., in the absence of inert liquid diluents.

In another modification, the supported catalyst-forming component isprepared by mixing the oxygenated Ti compound with an anhydrous Mghalide which has been activated by grinding prior to being mixed withthe Ti compound. However, in this case, the Ti compound and preactivatedMg halide are preferably mixed in suspension in an inert liquid diluent.

Anhydrous Mg halide in the required activated form may also be obtainedby methods other than grinding. One such method consists in startingwith a compound RMgX (in which R is a hydrocarbon radical and X ishalogen), and decomposing said compound RMgX by treating it with ahalogenated compound such as, for instance, gaseous hydrochloric acid,i.e. according to methods known in the literature.

The quantity of the oxygenated Ti compound used for preparing thesupported catalyst-forming component may be comprised within a widerange, the lower limit of which may be 0.01% by weight with respect tothe carrier or support and the upper limit of which may be 30% by weightor higher.

Particularly satisfactory results are obtained with respect to thepolymer yield referred both to the amount of Ti compound used and thecarrier or support when the amount of the Ti compound present on thecarrier is comprised between 1% and 10% by weight.

Hydrides and organometallic compounds which are particularly suited forthe preparation of the catalysts of this invention are:

Al(C₂ H₅)₃ ; Al(C₂ H₅)₂ Cl; Al(iC₄ H₉)₃ ; Al(iC₄ H₉)₂ Cl; Al(C₂ H₅)₂ H;LiC₄ H₉ ; Al(C₂ H₅)₂ Br; LiAl(iC₄ H₉)₄ ; Al(iC₄ H₉)₂ H and Al₂ (C₂ H₅)₃Cl₃.

The molar ratio between Al compound and the Ti compound is not critical.When the catalysts are to be used for the polymerization of ethylene,said ratio is preferably comprised between 50 and 1000.

The catalysts of the present invention can be used in the polymerizationor copolymerization of olefins by operating according to the knowntechniques, that is in liquid phase, in the presence or absence of aninert solvent, or in gaseous phase.

The temperature of the olefin polymerization or copolymerization incontact with the present catalysts is comprised between -80° and 200°C., preferably between 50° C. and 100° C., at either atmospheric orsubatmospheric pressure.

The molecular weight of the homopolymer or copolymer produced can beregulated, during the polymerization or copolymerization, by operatingin the presence of known molecular-weight regulating agents such as, forinstance, alkyl halides, organometallic compounds of zinc or cadium, orhydrogen.

As is known, the activity of the conventional "Ziegler catalysts"obtained by mixing transition metal compounds with organometalliccompounds of a Group I, II or III metal is considerably reduced by thepresence in the polymerization system of hydrogen or other chaintransfer agents which function as regulators of the molecular weight ofthe polymer or copolymer produced.

In contrast, we have found that it is possible to use the molecularweight-regulating agents for regulating the molecular weight of thepolymer or copolymer produced to low, and even very low values, in thepresence of the catalysts of this invention without any appreciablereduction in the activity of the catalysts.

For instance, it is possible in polymerizing ethylene in contact withthe present catalysts to regulate the molecular weight of thepolyethylene produced to values within a practical range correspondingto intrinsic viscosities for the polyethylene of between about 1.5 and3.0 dl/g. by including a known regulator of the molecular weight in thepolymerization system, without such a reduction in the yield ofpolyethylene obtained as to necessitate special purificationafter-treatments of the polymer for the removal of catalysts residuesfrom it. Any of the known molecular weight-regulators may be used withthe present catalysts.

Polyethylene obtained with the aid of the catalysts of this invention isa substantially linear, highly crystalline polymer having a density of0.96 g/cc. and processability characteristics which are in generalsuperior to those of the polyethylene obtained with conventional"Ziegler catalysts". The Ti content in the unpurified polyethylene isless than 20 ppm. Moreover, it has been discovered that, using acatalyst according to this invention, the polymer obtained has agranulometric distribution very similar to that of the starting(activated) carrier.

Thus, it is possible, by using a carrier or support suitably classifiedby screening to obtain polymers having a controlled granulometricdistribution. The preparation of the catalysts which polymerize theolefins to polymers of controlled granulometry may be carried out eitherby screening of the already supported catalytic component or byclassification of the carrier or support in active form, on whichcarrier or support the oxygenated Ti compound is then dispersed.

The following examples are given to illustrate the invention and are notintended to be limiting. Unless otherwise stated, the percentages givenin the examples are by weight. The intrinsic viscosities of the polymersgiven in the examples were measured in tetralin at 135° C.

EXAMPLE 1

0.706 g of TiCl₃ (O_(n) C₃ H₇) and 7.829 g of anhydrous MgCl₂ wereground in a nitrogen atmosphere for 20 hours, in a glass mill (length:100 mm; diameter; 50 mm), containing 550 g of steel balls with anindividual diameter of 9.5 mm.

0.0131 g of the mixture thus ground, suspended in 1500 cc of n-heptane,were introduced, together with 2 cc of Al(i--C₄ H₉)₃, in a nitrogenatmosphere, in a stainless steel autoclave of 3 liters holding capacity,fitted with a propeller stirrer and heated to a temperature of 80° C.

To this mixture was then ethylene (10 atm) and hydrogen (5 atm) and thetotal pressure of 15 atm was maintained constant throughout the test bycontinuously introducing ethylene.

After 8 hours the polymerization was stopped, the polymer obtained wasfiltered and then dried. Thereby were obtained 937 g of granularpolyethylene with an apparent density of 0.43 g/cc and an intrinsicviscosity determined in tetralin at 135° C., [η]=1.8 dl/g. The yield inpolymer amounted to 3,860,000 g/g of Ti.

EXAMPLE 2

In the mill described in Example 1, heated to 150° C., there were groundfor 18 hours 0.8110 g of Ti(O n--C₃ H₇)₄ and 10.5 g of anhydrous MgCl₂.

Using 0.066 g of this mixture and by conducting the polymerization ofthe ethylene according to the conditions described in Example 1. therewere obtained 120 g of polyethylene having an intrinsic viscosity,determined in tetralin at 135° C. [η]=2.4 dl/g.

The yield is polymer amounted to 150,000 g/g of Ti.

EXAMPLE 3

0.8535 g of TiCl₂ (O n--C₃ H₇)₂ and 10.201 g of anhydrous MgCl₂ wereground together for 18 hours at 20° C., under a nitrogen atmosphere, inthe mill as described in Example 1.

By using 0.0131 g of the ground mixture and by carrying out thepolymerization according to the procedures described in Example 1, therewere obtained 640 g of polyethylene having an intrinsic viscosity[η]=2.3 dl/g, determined in tetralin at 135° C.

The yield in polymer amounted to 950,000 g/g of Ti.

EXAMPLE 4

In a mill grinder as described in Example 1, heated to a temperature of150° C., there were ground for 20 hours 1,340 g of TiCl(O--n--C₃ H₇)₃and 10.7162 g of anhydrous MgCl₂.

By using 0.0420 g of this ground mixture and by operating according towhat described in Example 1, there were obtained 110 g of polyethylenehaving an intrinsic viscosity, determined in tetralin at 135° C.,[η]=2.22 dl/g. The yield in polymer amounted in 162,000 g/g of Ti.

EXAMPLE 5

0.9125 g of TiCl₃ (O n--C₃ H₇) and 7.9102 g of anhydrous MgBr₂ wereground for 20 hours at 20° C. in a mill as described in Example 1.

By using 0.0151 g of the mixture thus prepared and by carrying out thepolymerization of the ethylene according to the procedures described inExample 1, there were obtained 475 g of polyethylene having an intrinsicviscosity, determined in tetralin at 135° C., [η]=1.88 dl/g. The yieldin polymer was 1,350,000 g/g of Ti.

EXAMPLE 6

1.0 g of TiCl₃ (OC₆ H₅) and 9.4510 g of anhydrous MgCl₂ were ground for18 hours at 20° C. and under a nitrogen atmosphere in the mill describedin Example 1. By using 0.0119 g of this mixture and operating accordingto Example 1, there were obtained 429 g of polyethylene having anintrinsic viscosity, determined in tetralin at 135° C., [η]=1.49 dl/g.The yield in polymer amounted to 1,950,000 g/g of Ti.

EXAMPLE 7

7.13 g of Ti(On--C₃ H₇)₄ dissolved in 10 cc of anhydrous xylol were madeto react in a nitrogen atmosphere with 3.9 g of titanium trichloride, ata temperature of 120° C., in a flask of 25 cc holding capacity, providedwith a stirrer.

After 12 hours, the resulting suspension was filtered, the solid wasrepeatedly washed with n-heptane and finally dried. Thereby, wereobtained 4 g of a brown powdery product, which at the elementaryanalysis showed the following composition: Ti₂ Cl₃ (On--C₃ H₇)₃. Thetitanium present in the compound proved to have a valency=3.

0.800 g of Ti₂ Cl₃ (On--C₃ H₇)₃, prepared as above, were ground in anitrogen atmosphere together with 7.241 g of anhydrous MgCl₂ in the milldescribed in Example 1.

By using 0.096 g of this mixture and by operating according to theprocedures described in Example 1, but interrupting the polymerizationafter 5 hours, there were obtained 810 g of polyethylene having anintrinsic viscosity, determined in tetralin at 135 C, [η]=1.68 dl/g. Theyield in polymer amounted to 336,000 g/g of Ti.

EXAMPLE 8

In the mill described in Example 1, heated to 130° C., there were groundfor 20 hours, in a nitrogen atmosphere, 1.210 g of titaniumtrichloroacetylacetonate [TiCl₃ (C₅ H₇ O₂)] and 8.620 g of anhydrousMgCl₂.

Using 0.0179 of this mixture and carrying out the polymerization of theethylene according to the procedures described in Example 1, there wereobtained 362 g of polyethylene having an intrinsic viscosity determinedin tetralin at 135° C. [η]=2.14 dl/g. The yield in polymer amounted to930,000 g/g of Ti.

EXAMPLE 9

In the mill described in Example 1, there were ground, for 20 hours in anitrogen atmosphere at 20° C., 0.825 g of TiCl(OCO--CH₃) and 8.135 g ofanhydrous MgCl₂.

Using 0.0127 g of this mixture and operating according to the proceduresof Example 1, there were obtained 280 g of polyethylene having anintrinsic viscosity, determined in tetralin at 135° C., [η]=2.01 dl/g.The yield in polymer amounted to 1,065,000 g/g of Ti.

EXAMPLE 10

In the mill described in Example 1, there were ground for 20 hours in anatmosphere of nitrogen at 20° C., 0.9734 g of TiCl₃ (OCOC₆ H₅) and10.5718 g of anhydrous MgCl₂.

Using 0.0138 g of this mixture and operating according to the proceduresdescribed in Example 1, there were obtained 375 g of polyethylene havingan intrinsic viscosity, determined in tetralin at 135° C., [η]=2.20dl/g. The yield in polymer amounted to 1,855,000 g/g of Ti.

EXAMPLE 11

In the mill described in Example 1, there were ground, for 20 hours in anitrogen atmosphere at 0° C., 1.0828 g of TiBr₃ (On--C₃ H₇) and 9.870 gof anhydrous MgCl₂.

Using 0.0128 g of this mixture and operating according to the proceduresdescribed in Example 1, there were obtained 352 g of polyethylene havingan intrinsic viscosity, determined in tetralin at 135° C., [η]=1.59dl/g. The yield is polymer amounted to 2,015,000 g/g of Ti.

EXAMPLE 12

In a rotary ball mill of the centrifugal type there were ground, for 3hours, 0.038 g of TiCl₃ OCH₃ and 10 g of anhydrous MgCl₂.

Using 0.15 g of the ground mixture and operating according to theprocedures described in Example 1, for 4 hours, there were obtained 125g of polyethylene having an intrinsic viscosity [η]=2.9 dl/g. The yieldin polymer amounted to 1,250,000 g/g of Ti.

EXAMPLE 13

Under the same conditions as those indicated in Example 12, there wereground 1 g of Ti(On--C₄ H₉)₄ and 13 g of anhydrous MgCl₂.

Using 0.16 g of this ground mixture and by operating under the samepolymerization conditions of Example 12, there were obtained 220 g ofpolyethylene having an intrinsic viscosity [η]=2.5 dl/g. The yield inpolymer amounted to 182,000 g/g of Ti.

EXAMPLE 14

In the mill and under the same conditions as described in Example 12there were ground, for 3 hours, 0.28 g of TiCl₃ (O--2-ethylhexyl) and 10g of anhydrous MgCl₂.

Using 0.2283 g of the ground mixture and by polymerizing ethylene underthe same conditions as those described in Example 12, there wereobtained 445 g of polyethylene having an intrinsic viscosity [η]=2.0dl/g. The yield in polymer amounted to 780,000 g/g of Ti.

EXAMPLE 15

In the mill of Example 12, there were ground together for 3 hours 0.20 gof TiCl₃ (OC₁₀ H₇) (obtained from TiCl₄ +beta-naphol) and 10 g ofanhydrous MgCl₂.

Using 0.1228 g of the ground product and operating under the samepolymerization conditions as those described in Example 12, there wereobtained 300 g of polyethylene having an intrinsic viscosity [η]=2.0dl/g.

EXAMPLE 16

Under the same conditions as those described in Example 12, there wereground together 0.1 g of TiCl₃ (OC₆ H₄ NO₂) and 10 g of anhydrous MgCl₂.Using 0.083 g of the mixture thus ground and by polymerizing under theconditions of Example 12, there were obtained 91 g of polyethylenehaving an intrinsic viscosity [η]=2.6 dl/g, while the yield in polymeramounted to 842,000 g/g of Ti.

EXAMPLE 17

Operating under the same conditions as those of Example 12, 0.1 g ofTiCl₃ (OC₆ H₄ Cl) and 10 g of anhydrous MgCl₂ were ground together.Using 0.109 g of the ground mixture and polymerizing ethylene in contactwith the ground mixture, under the polymerization conditions of Example12, there were obtained 271 g of polyethylene having an intrinsicviscosity [η]=2.2 dl/g. The yield in polymer amounted to 2,480,000 g/gof Ti.

EXAMPLE 18

6.2 g of ethylene glycol were reacted in a reflux reactor for 3 hourswith 11.3 g of TiCl₄ dissolved in 100 cc of n-heptane.

The solid product thus formed was separated, washed with n-heptane andfinally dried under vacuum. The analysis gave the following composition:Ti=17.15%; Cl=39.2%.

0.45 g of the Ti-chloroalcoholate thus prepared and 10 g of anhydrousMgCl₂ were ground together under the conditions of Example 12.

Using 0.1048 g of the ground product and polymerizing ethylene under theconditions of Example 12, there were obtained 226 g of polyethylenehaving an intrinsic viscosity [η]=1.5 dl/g. The yield in polymeramounted to 280,000 g/g of Ti.

EXAMPLE 19

In a ball mill there were ground together for 3 hours, 10 g of anhydrousMgCl₂ and 0.35 g of TiCl₃ (OiC₃ H₇). The ground product was thenclassified granulometrically on a vibrating screen or sieve, in an inertatmosphere. The fractions which were drawn from it were:

    Fraction 1>0.044 mm<0.062 mm

    Fraction 2>0.088 mm<0.125 mm

Into a 1.8 liter autoclave there was then introduced 1 liter ofn-heptane and 2.0 g of Al(iC₄ H₉)₃. This mixture was brought up to 85°C. and 0.11 g of fraction 1 of the supported catalytic component wasintroduced while the pressure was brought up to 4 atm. by means of H₂and then to 13 atm. by feeding in ethylene.

The pressure was maintained constant at 13 atm. by feeding in ethylene.After 3 hours of reaction, there were discharged 355 g of polymer havingan intrinsic viscosity [η]=2.2 dl/g. The yield in polymer amounted to357,000 g/g of Ti.

In the same conditions above indicated, by using 0.11 g of the fraction2 of the catalytic component, 347 g of polymer were obtained havingintrinsic viscosity [η]=2. Polymer yield 347,000 g/g of Ti.

By fractioning on a vibrating screen the following granulometricdistribution of the polymers thus prepared was obtained.

                  TABLE                                                           ______________________________________                                                         Polymer % Polymer %                                          Net light of the screen                                                                        Fraction 1                                                                              Fraction 2                                         ______________________________________                                        >2    mm         --        27.5                                               >1.41  mm <2   mm                                                                              0.8       66.0                                               >1.0  mm <1.41 mm                                                                              24.6      5.1                                                >0.71  mm <1.0  mm                                                                             47.9      1.0                                                >0.5  mm <0.71 mm                                                                              15.9      0.3                                                >0.35  mm <0.5  mm                                                                             5.5       0.1                                                >0.177 mm <0.35 mm                                                                             4.5       0.1                                                >0.177           0.9        0.05                                              ______________________________________                                    

We claim:
 1. Highly active catalysts for the polymerization of olefinsand obtained by mixing(a) a catalyst-forming component which is ahydride or organo-metallic compound of a metal belonging to one ofGroups I to III inclusive of the Mendelyeev Periodic Tablewith (b) asupported catalyst-forming component obtained by contacting a titaniumcompound containing organic radicals bound to oxygen through a carbonatom and in which at least one Ti atom is bound through the oxygen atomto the organic radical, any valency of the Ti atom not satisified byorganic radicals bound to oxygen through the carbon atom being satisfiedby halogen, with a carrier comprising an anhydrous magnesium dihalide inan active form characterized in that its X-ray powder spectrum does notshow the most intense diffraction line as it appears in the X-ray powderspectrum of the normal, non-active magnesium dihalide, the spectrum ofthe active magnesium dihalide showing a broadening of said most intensediffraction line.
 2. Catalysts according to claim 1, characterized inthat the amount of the titanium compound on the carrier is from 0.01% to30% by weight.
 3. Catalysts according to claim 1, characterized in thatthe amount of the titanium compound on the carrier is from 1% to 10% byweight.
 4. Catalysts according to claim 1, characterized in that theanhydrous magnesium dihalide is anhydrous magnesium dichloride. 5.Catalysts according to claim 1, characterized in that the anhydrousmagnesium dihalide is anhydrous magnesium dibromide.
 6. The method ofpreparing catalysts which are highly active in the polymerization ofolefins which consists of mixing(a) a catalyst-forming component whichis a hydride or organo-metallic compound of a metal belonging to one ofGroups I to III inclusive of the Mendelyeev Periodic Tablewith (b) asupported catalyst-forming component obtained by contacting a titaniumcompound containing organic radicals bound to oxygen through a carbonatom and in which at least one Ti atom is bound through the oxygen atomto the organic radical, any valency of the Ti atom not satisfied byorganic radicals bound to oxygen through the carbon atom being satisfiedby halogen, with a carrier comprising an anhydrous magnesium dihalide inan active condition characterized in that its X-ray powder spectrum doesnot show the most intense diffraction lines as it appears in the X-raypowder spectrum of the normal, non-active magnesium dihalide, thespectrum of the active magnesium dihalide showing a broadening of saidmost intense diffraction line.
 7. The method according to claim 6, inwhich catalyst-forming component (b) is obtained by cogrinding thetitanium compound with a starting magnesium dihalide in its normalnon-activated condition.
 8. The method of claim 7, wherein theco-grinding of the titanium compound and anhydrous magnesium dihalide iscarried out in a ball mill, in the absence of inert liquid diluents. 9.The method according to claim 6, in which catalyst-forming component (b)is obtained by contacting the titanium compound with an anhydrousmagnesium dihalide in preactivated condition.
 10. The method accordingto claim 6, in which catalyst-forming component (b) is obtained bycontacting the titanium compound with a preactivated magnesium dihalidewhich is the decomposition product of an organo-metallic compound offormula RMgX, in which R is a hydrocarbon radical and X is halogen. 11.A process for the catalytic polymerization of ethylene to a linear,highly crystalline polyethylene useful as produced without requiringspecial purifying after-treatments for the removal of catalyst residuestherefrom, which comprises polymerizing the ethylene in contact with acatalyst according to claim
 1. 12. The process of claim 11, wherein theethylene is polymerized in contact with a catalyst according to claim 1and in the presence of a regulator of the molecular weight of thepolyethylene produced.